C Language Programming Library
Reference Guide

stdlib.h -
Math Functions - ldiv

Declaration:
ldiv_t ldiv(long int numer,
long int denom);
Divides numer (numerator) by denom (denominator).
The result is stored in the structure ldiv_t
which has two members:
long int qout;
long int rem;
Where quot is the quotient and rem is the
remainder. In the case of inexact division, quot is
rounded down to the nearest integer. The value numer is
equal to quot * denom + rem.